Abstract: An electric lamp includes a sealed lamp envelope including a dome region having an inward projection and a neck region sealed to a lamp stem. A lamp subassembly is located within the lamp envelope and includes an arc tube for generating light when electrical energy is applied thereto. A generally cylindrical, light-transmissive shroud is disposed about the arc tube. A frame includes a single support rod extends between the dome and neck regions of the lamp envelope along one side only of the subassembly, and a dome end of the frame engages the inward projection of the lamp envelope. A mounting structure is provided for attaching the arc tube and shroud to the frame. A bulb spacer is provided having first and second segments bearing against an inside surface of the lamp envelope in the neck region for positioning the frame relative to the lamp envelope, and also having a third segment joining the first and second segments, the third segment being spaced away from the inside surface of the lamp envelope.

Abstract: A line-of-sight arched arc tube of an arc discharge lamp; e.g., a metal halide arc discharge lamp for horizontal operation having an arched upper wall to accommodate the bowing of the arc discharge during full temperature and pressure operation of the lamp and a lower wall of lesser curvature to accommodate the arc discharge during lamp start and warm-up. The curvature of the lower wall is such that there is a straight line-of-sight between the primary electrodes without being impeded by the lower wall of the arc tube and such that temperature profiles over the body of the arc tube are optimized during full temperature and pressure operation of the lamp.

Abstract: A high-pressure metal halide arc discharge lamp having an arc tube with a pair of main electrodes disposed within the tube at opposite ends and a starting electrode located adjacent one of the main electrodes. A tubular sleeve of insulating material, such as quartz, is disposed about the starting electrode, which is recessed within the sleeve but exposed through the open end thereof to the interior atmosphere of the arc tube. Since the starting electrode does not project beyond the open end of the sleeve, conduction between that electrode and the adjacent main electrode is minimized or prevented during normal lamp operation, thereby minimizing or preventing electrolysis.